Prosthetic implant devices are well known for the purpose of completely or partially replacing existing skeletal joints in the human body. In the human foot, the metatarsophalangeal joint between the first metatarsal and the first phalanx, in what is commonly known as the hallux or great toe is the site of frequent occurrences of arthritic deterioration. As a result, much attention has been directed to full or partial replacement of the joint.
One technique known for partial replacement of the joint uses silicone based materials attached to the phalanx. When such material is in contact with the metatarsal head, however, these types of implants eventually break down, reducing their effectiveness and potentially damaging surrounding tissues. Likewise, attempts at full joint replacement using silicone material have produced results which are less than desirable.
Metal implant devices, typically of titanium, have been adopted as preferable substitutions for flexible silicone materials. Joint replacement may be full or partial (hemi). Where the metatarsal head remains intact, manageable results have been achieved by providing a metal implant device fixed to the phalanx head of the joint. It is generally not acceptable to replace both sides of the joint with metal implants, a procedure which frequently results in either joint discomfort or progressive dislocation of the joint, or both.
Hemi joint replacement is the preferred surgical procedure in cases where the metatarsophalangeal joint has deteriorated, while the metatarsal head remains intact. This procedure is generally indicated where the patient experiences painful arthritis or hallux valgus. A typical example of a hemi-implant for replacing a phalanx in the hallux is disclosed in U.S. Pat. No. 5,326,366 issued to Pascarella et al., entitled “Biomechanical Great Toe Implant”.
Other joint replacement techniques involve full replacement of the joint, for example, as taught in U.S. Pat. No. 5,458,648 to Berman et al.; U.S. Pat. No. 5,314,486 issued to Zang et al.; and U.S. Pat. No. 6,699,292 issued to Ogilvie et al.
A known difficulty with using hemi implants in the metatarsophalangeal joint, however, is that hemi implants may cause deterioration of the nearby interphalangeal joint. For this reason, many surgeons will not use a hemi implant to partially replace the metatarsophalangeal joint.
A further solution to the problem, particularly useful in arthritic joints, is fusion of the distal phalanx and proximal phalanx, in conjunction with a hemi implant. By fusing the distal and proximal phalanxes as taught herein, a solid lever arm is created, thereby improving articulation between the first metatarsophalangeal joint and the proximal phalanx.